Suspension Upgrade

nvestysly

Looking for
I installed Bilstein B6 shocks on the rear of our 2008 3500 today. Took a few hours total - not too difficult - and it gave me a chance to look around under the van. We've recently purchased this 2010 Interstate (on a 2008 chassis) so we're still learning about the systems and how things operate, where things are located, etc.

Back to the shocks... I won't have a chance to drive the van for another week or so because I want to leave it up on the jack stands until I've completed some other under-body upgrades. I'll take time to post after I test drive. I'm sure hoping the rocking is reduced.
 

Philip53

2021 2500 Sprinter 170, 4 cyl gas
I want to back up Calbiker in his posts regarding Fox shocks. They do a wonderful job taming the rocking motion on my '17 Navion J, improves tracking in the turns and helps stability in high crosswinds . From all that I have heard on this forum, if you are considering shocks, seriously look at the Agile modified Fox shocks--they are much, much better than what comes on the RV--absolutely no comparison. I have also added the Supersprings SSA-111 helper springs on the back, sumos on the front, and just recently installed the Kelderman 2-stage rear air suspension. The ride I now have, I believe, is the best I can expect without going to a full air system such as VB or Glide-Rite. If I had the knowledge then that I have now, I probably would have skipped everything else and installed the Glide-Rite system, front sumos and Fox shocks, and skipped everything else.

And on the sway bar issue, I have had a bad experience when installing one on the front of a Super C motorhome several years back. On that RV, I had added an air bag system on the front and got an immediate better, more supple ride. I then added a sway bar and the ride went to $hi!. I guess it was so strong that it simply locked up the front end and really screwed up the ride. It was more stable though, but with a much harsher ride penalty.

Hope this helps someone with their suspension decisions.........
 
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nvestysly

Looking for
Yes, the Bilstein B6 rear shocks the rocking! It's difficult to have an precise feel for how much the rocking (roll) is reduced because it was over two weeks ago that I last drove the van. My seat of the pants meter indicates the shocks make an improvement.

Going over a curb, angled speed bump or something similar continues to make the van rock one way or another - that can't be eliminated - I'm going over a bump after all. What is reduced is the subsequent rocking due to underdamped factory shocks. The Bilstein B6's definitely help eliminate the secondary rock/roll factor. The Fox Shocks may do better but the Bilsteins were in stock at Summit Racing and shipped immediately.

Next up is the B6 struts for the front... but that may be a month or two from now.
 

calbiker

Well-known member
I see some are installing the Bilstein 24-177702 (B6) shock. I had tested them and found them somewhat improved over the OEM shocks, but not enough improvement for me. My testing is not subjective, but consists of accelerometer data recording. Putting the data into an Excel spreadsheet and then calculating damping and other analysis. The Fox shocks from Agile were by far the best shock for heavy motor homes. I had also tested Monroe, and Koni reds.

I want to back up Calbiker in his posts regarding Fox shocks.
 

EQuest

New member
Calbiker - Thank you for the info on the Agile tuned Fox shocks. My only question is have you tested /compared them to the new Koni FSD shocks. I need to improve the ride & handling on my motor home as my wife has a bad back.
Thank you for any help.
Bill D
 

calbiker

Well-known member
I have not tested the Koni FSD shocks. I doubt they are better than the Reds. The purpose of shocks is to throttle or damp the energy in the springs. If there are no dampers, the chassis will bounce many cycles. In fact I have removed the OEM shocks and found they do little to throttle oscillations. My testing measures the damping ratio. The damping ratio is a measure to what extent the following peak amplitude is reduced after the spring is energized. I like to see a damping ratio of 0.2, but my '06 Sprinter MH has damping of <0.1 (see green graph plot for reference). A damping factor of 0.1 causes the MH to be pushed around by passing trucks (or wind) and causes severe rocking when entering driveways or traveling uneven dirt roads. The suspension becomes volatile.



The modified Fox shocks are your best bet to tame the suspension.

Shocks do nothing to cure the jarring effects of freeway expansion joints. That's not the function of shock absorbers. The springs are not subtle enough to react to these conditions. Air bags are known to help in these conditions. Air bags in parallel to the springs will not help (much). The steel spring is still active.

Your best bet (besides Fox shocks) is the Kelderman 2-stage rear air suspension. This suspension mod disengages the steel leaf springs for small jarring shocks like expansion joints. The air bags take up these shocks, reducing the effects inside the MH. Take a look at Philip53 install/review thread.
 

ArtistWithAView

2017 View J
Calbiker - Thank you for the info on the Agile tuned Fox shocks. My only question is have you tested /compared them to the new Koni FSD shocks. I need to improve the ride & handling on my motor home as my wife has a bad back.
Thank you for any help.
Bill D
I had the Koni FSD shocks and they were an improvement over stock. I then ordered and installed the Agile Fox shocks and what a difference! So much better than the Koni. The rock is all bit gone.

Steve
2017 View J
 

Yaroslav

2015 Sprinter 3500
Hello guys,
I installed rear SumoSprings in May, and the ride is much better cornering on the highway speeds.
Bought the new Koni, red, not adjustable, part number 1058 (just released). Will report once receive and installed.
Safe trips!
 

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